The present invention relates to a control device for directing an antenna disposed on a movable body such as aircraft, vehicles, ships or the like to a wave generating source.
In satellite communication systems using an antenna disposed on movable body, the antenna is controlled to track the satellite under consideration of the movable body's location and change of the movable body's attitude, since it is necessary at all times to direct the antenna to the satellite.
As a prior art for antenna tracking control described above, an invention disclosed in Japanese Patent Laid-Open No. 271182 (1988) is explained below.
FIG. 5 is a block diagram showing an example of a body tracking control device of antenna loaded on movable body. Where, 51 is an antenna, 52 is an antenna directing angle error detector, 53 is a movable body azimuth angle detector, 54 is an antenna directing angle error corrector, 55 is an antenna tracking controller and 56 is an antenna driving motor.
First of all, the antenna directing angle error detector 52 calculates a difference between satellite direction and antenna beam direction, that is, antenna directing error and outputs an antenna directing angle error signal x.
On the other hand, the movable body azimuth angle detector 53 detects azimuth angle of the movable body and outputs a movable body azimuth angle signal y.
The antenna directing angle error corrector 54 inputs the antenna directing angle error signal x and the movable body azimuth angle signal y, corrects the antenna directing angle error signal x using the movable body azimuth angle signal y and outputs an antenna directing angle error correction signal z.
Then, the antenna tracking controller 55 controls the antenna driving motor 56 to direct the antenna 51 to the satellite, based on the antenna directing angle error correction signal z.
Providing for a case that the antenna directing angle error detector 52 cannot detect the antenna directing angle error signal x, a number of satellites' orbit data, as well as the antenna directing angle error signal x, are prepared in advance for the antenna tracking controller 55.
Only when input of the antenna directing angle error signal x is stopped, the antenna tracking controller 55 controls the antenna driving motor 56 using a pseudo antenna error signal generated from the satellites' orbit data and the movable body azimuth angle signal y.
In the above-mentioned art for controlling tracking of antenna loaded on a movable body, however, detection of azimuth angle of a movable body when the movable body changes advancing direction is delayed in the movable body azimuth angle detector 53. If the movable body is an automobile, for example, at the time when the handle is operated to steer tires, azimuth angle of the automobile is not changed yet because the automobile does not move enough. Therefore, it is not possible at this time to anticipate and detect advancing azimuth angle of the automobile.
In this system, if the antenna directing angle error signal x is corrected using the azimuth angle detected by the movable body azimuth angle detector 53, it is not possible to correct it without any time lag due to time needed for correction processing, etc.
In addition, antenna tracking response speed of such an art is limited by a dead time of the antenna tracking controller 55 and a time lag in the antenna directing angle error detector 52.